Apparatus for detecting and indicating the balance of a rotary body in a machine tool

ABSTRACT

The present invention relates to an apparatus for detecting and indicating the balance of a rotating body such as a grinding wheel, a spindle or the like in a machine tool such as a grinding machine. The apparatus comprises an original-point detecting means for detecting an original point on the rotating body, a vibration detecting means for detecting vibration caused by an unbalanced condition of the rotating body, an arithmetic means for computing, from the detected vibration, a deviation of said rotating body in each of a plurality of index positions on the rotating body which are angularly spaced from said original point as a reference, a deviation display means for displaying the maximum value of the deviations, and an unbalanced position indicating means for indicating one of the index positions based on the computed deviations.

This application is a continuation of application Ser. No. 778,577,filed Sept. 20, 1985, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the invention:

The present invention relates to an apparatus for detecting andindicating the balance of a rotating body such as a grinding wheel, aspindle or the like in a machine tool such as a grinding machine bydetecting and indicating the amount of off-center deviation of therotating body.

2. Description of the Prior Art:

Some machine tools employed for machining workpieces have spindlessupporting rotating tools for machining the workpieces. Should therotating tool attached to the spindle be unbalanced or the pulley andgears in the machine tool for driving the spindle be unbalanced, thespindle would be rotated eccentrically or out of trueness, and theworkpiece would not be machined with trueness in its bore or on itsouter periphery. Where the machine tool of this type is used formachining the workpiece with high accuracy, it is necessary to detectthe amount of an off-center deviation of the spindle and correct it intoproper balance. Especially in grinding machines, the rotating tool orgrinding wheel is required to be properly balanced for accurate grindingoperation.

For adjusting the rotational balancing of a grinding wheel, it has beencustomary to attach the grinding wheel to a single shaft placed over twohorizontal bars, detect the direction and speed of rolling movement ofthe grinding wheel as it rolls of its own accord for determining theposition and amount of eccentricity of the grinding wheel, and correctthe grinding wheel to balance the same properly based on the determinedoff-center position and amount. However, such a balance correctingprocess relies on the worker's skill and hence is not sufficientlyefficient. The conventional balance correcting process is not concernedwith the correction of any unbalance of the shaft by which the grindingwheel is supported. Therefore, even when the grinding wheel is properlybalanced, it will be rotated out of balance if attached to an unbalancedshaft.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus fordetecting and accurately indicating the balance of a rotating body as itis attached to a machine tool.

Another object of the present invention is to provide an apparatus fordetecting and indicating the balance of a rotating body in a machinetool, the apparatus having a detector and indicator device associatedwith the machine tool for allowing the operator to monitor the balancecondition of the rotating body at all times.

Still another object of the present invention is to provide an apparatusfor detecting and indicating the balance of a rotating body in a machinetool, the apparatus having a means for enabling the operator to confirmthe balance condition of the rotating body at a glance.

A still other object of the present invention is to provide an apparatusfor detecting and indicating the balance of a rotating body in a machinetool by selecting only the vibration of the rotating body from thevibration of the overall machine tool for detecting the amount of anoff-center deviation of the rotating body dependent on the r.p.m.thereof.

A still further object of the present invention is to provide anapparatus for detecting and indicating the balance of a rotating body ina machine tool by automatically selecting only the vibration of therotating body from the various vibrations of the machine tool fordetecting the amount of an off-center deviation of the rotating bodydependent on the r.p.m. thereof.

Still another object of the present invention is to provide an apparatusfor detecting and indicating the balance of a rotating body in a machinetool by selectively detecting and indicating the overall vibration ofthe machine tool and the vibration of the rotating body such as aspindle.

A still other object of the present invention is to provide an apparatusfor detecting and indicating the balance of a rotating body in a machinetool, the apparatus having a means for correcting an indicatedunbalanced position of the rotating body into an actual unbalancedposition thereof based on a phase variation when the indicated andactual unbalanced positions are not in exact conformity with each other.

The above objects can be achieved by an apparatus for detecting andindicating the balance of a rotating body in a machine tool, theapparatus having an original detecting means for detecting the originalposition of the rotating body, a vibration detecting means for detectingthe vibration of the rotating body arising from an unbalanced conditionthereof, an arithmetic means for computing, based on the detectedvibration, off-center deviations of the rotating body in respectiveindex positions with the original position serving as a referenceposition therefor, and an unbalanced position indicating means forindicating the index positions based on the computed off-centerdeviations.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which preferredembodiments of the present invention are shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a block diagram of an apparatus according to the presentinvention;

FIG. 1b is a diagram showing the principles of operation of theapparatus;

FIG. 2a is a side elevational view of a surface grinder;

FIG. 2b is a perspective view of a vibration detector;

FIG. 3 is a front elevational view of a balance detecting and indicatingapparatus according to a first embodiment of the present invention;

FIG. 4 is a block diagram of an electric circuit of the balancedetecting and indicating apparatus shown in FIG. 3;

FIG. 5 is a circuit diagram of a filter circuit;

FIGS. 6 and 7 are a flowchart of operation of the balance detecting andindicating apparatus;

FIG. 8 is a flowchart of operation of a balance detecting and indicatingapparatus according to a second embodiment of the present invention; and

FIG. 9 is a circuit diagram of a portion of a filter circuit in thesecond embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention will be described withreference to FIGS. 1a through 7.

A surface grinder in which a balance detecting and indicating apparatusof the first embodiment is incorporated will first be described brieflywith reference to FIGS. 2a and 2b. A table 2 for holding a workpiece Wis movably mounted on a frame 1. A spindle 3 is rotatably supported overthe table 2, and a grinding wheel 4 is attached to an end of the spindle3 in confronting relation to the workpiece W. A motor 5 for driving thespindle 3 is connected to the other end of the spindle 3.

A grinding wheel head 6a is vertically movably attached in acantilevered fashion to a column 6 of the frame 1. On the distal end ofthe grinding wheel head 6a, there is detachably mounted a piezoelectricacceleration pickup 7 (FIG. 2b) serving as a vibration detecting means.To the bottom of the piezoelectric acceleration pickup 7, there is fixeda spacer 37 in the form of an iron or aluminum plate. A magnet 36 issecured to the bottom of the spacer 37. The acceleration pickup 7 istherefore magnetically attracted to the grinding wheel head 6a by themagnet 36. The spacer 37 may be dispensed with. The acceleration pickup7 may be bolted to the grinding wheel head 6a, rather than magneticallyattracted thereto by the magnet 36. The frame 1 includes all of thoseparts except those which are rotated by the motor 5. The accelerationpickup 7 may be located anywhere on the frame 1 insofar as it can detectvibration of the spindle 3 or the magnet 4.

The deviation or displacement of the frame 1 is produced by the overallvibration of the surface grinder, which is the sum of various vibrationsof the movable components of the surface grinder, i.e., the table 2, thespindle 3, the grinding wheel 4, the motor 5, and the like.

A light reflecting body 8 serving as a piece to be detected is attachedto the front face of the grinding wheel 4 for rotation therewith. Anoriginal-point detecting sensor 10 serving as an original-pointdetecting means is supported by a stand 9 in a position confronting thearea or plane in which the light reflecting body 8 rotates. Theoriginal-point detecting means may be constructed differently. Forexample, the light reflecting body 8 may be dispensed with, and a pieceto be detected may project from the spindle 3 for rotation therewith,and a photosensor may be positioned as an original-point detecting meanson the frame 1 in confronting relation to the piece to be detected.

The balance detecting and indicating apparatus coupled to the surfacegrinder of the above construction will be described below. As shown inFIG. 3, an indicating device 12 has a front surface serving as anindicating section 13 on which a total of 36 index-position indicators14 are arranged in an annular pattern and angularly spaced at 10-degreeintervals. An original-point indicator 15 is positioned in radiallyconfronting relation to the 0-degree index-position indicator 14. Anumerical display 16 is positioned centrally on the indicating section13 for numerically displaying the off-center deviation of the grindingwheel 4 and the r.p.m. of the spindle 3, each numeral being displayed bya 7-segment LED or liquid crystal assembly.

On the lower end of the indicating section 13, there are disposed threelow-, medium-, and high-gain setting switches 17 for setting theamplification degrees of a signal detected by the acceleration pickup 7,a changeover switch 18 for displaying the r.p.m. of the spindle 3 on thenumerical display 16, and a hold switch 19 for holding the display onthe numerical display 16 and the indication on the index-positionindicators 14. Indicators 17a, 18a, 19a are located respectively abovethe switches 17, 18, 19 for confirming the operation of the switches 17,18, 19.

A position controller 21 is disposed as a correcting means on one sideof the lower end of the indicating section 13. The position controller21 has a pair of numerical rings 23 exposed through a window 22, eachnumerical ring 23 having an integral operating portion 23a of aroughened surface for rotating the numerical ring 23. Above the positioncontroller 21, there are positioned a mode selector switch 35 forselecting one, at a time, of an adjustment mode including correction ofthe indicated position on the index-position indicators 14 and a balancemeasurement mode, and a condition setting switch 36 for setting acondition indicative of whether an unbalance-generating weight isattached or not in the adjustment mode. Based on the indicated-positioncorrecting data in the adjustment mode, the numerical rings 23 of theposition controller 21 are turned through appropriate intervals forcorrecting the indicated position on the index-position indicators 14 inincrements of 10 degrees. Denoted at 20 in FIG. 3 is a power supplyswitch.

An electric circuit of the balance indicating apparatus according tothis embodiment will be described with reference to FIG. 4. To a centralprocessing unit (CPU) 24 including an arithmetic means, a selectingmeans, and a control means, there are connected a read-only memory (ROM)25 for storing a program which controls the operation of the overallapparatus, and a random-access memory (RAM) 26 having a data area forstoring data. The CPU 24 is connected to an input/output interface 27having input terminals to which there are coupled the piezoelectricacceleration pickup 7 through an A/D converter 28 and a filter circuit29, the original-point detecting sensor 10, the hold switch 19, the gainsetting switches 17, the changeover switch 18, the position controller21, the mode selector switch 35, and the condition setting switch 36.The input/output interface 27 has output terminals connected to theindex-position indicators 14, the original-point indicator 15, thenumerical display 16, and the confirming indicators 17a, 18a, 19a. Whenthe changeover switch 18 is operated, the CPU 24 detects the r.p.m. ofthe spindle 3 and the grinding wheel 4 based on the interval oforiginal-point pulses issued from the original-point detecting sensor 10and enables to display the detected r.p.m. on the numerical display 16.

The filter circuit 29 serves to detect the vibration of the grindingwheel head 6a through the acceleration pickup 7 and detects only thevibration of the spindle 3 and the grinding wheel 4 from the detectedvibration of the grinding wheel head 6a. As shown in FIG. 5, the filtercircuit 29 is composed of a charge amplifier circuit 30 for convertingthe charge of the acceleration pickup 7 to the voltage of anacceleration signal SG1, a voltage amplifier circuit 31 for adjustingthe vibration sensitivity with a rheostat R1, an integrating circuit 32for converting the acceleration signal SG1 to a speed signal SG2, abandpass filter (B.P.F.) 33 for selecting a required signal, and a gainswitching amplifier circuit 34 for switching an amplification degree forthe speed signal SG2 based on the operation of the gain setting switch17. The bandpass filter 33 is supplied with an adjustment signal SG3from the CPU 24 via the input/output interface 27 for bringing thecentral frequency of the filter 33 into conformity with the frequencycorresponding to the r.p.m. of the spindle 3 as detected by coaction ofthe original-point sensor 10 and the CPU 24.

Operation of the balance indicating apparatus thus constructed will bedescribed below. FIGS. 6 and 7 are a flowchart of the program executedby the CPU 24.

As shown in FIG. 6, when the power supply switch 20 of the indicatingdevice 12 is turned on, initialization is effected in a step S1 and thena step S2 ascertains whether the adjustment mode is selected by the modeselector switch 35. If the adjustment mode is not set, then the programgoes through a step S3 to a step S15 (FIG. 7) for balance measurementand indication.

If the adjustment mode is selected in the step S2, then the programproceeds to a step S4 which determines how the condition setting switch36 is operated. Assuming that the spindle 3 is to be rotated with noweight attached to the grinding wheel 4 according to the procedure, andif the condition setting switch 36 is shifted to a weight position, thenan operation error is displayed on the numerical display 16 in a stepS5. If the condition setting switch 36 is properly shifted to anon-weight position, then control goes to a step S6 which ascertainswhether the rotation of the spindle 3 and the grinding wheel 4 is stableor not by measuring and comparing the intervals of original-pointdetecting pulses issued from the original-point detecting sensor 10. Ifthe rotation of the spindle 3 and the grinding wheel 4 becomes stable,then the program enters a measurement and indication routine in a stepS7 in which the step S15 and following steps are executed as describedlater on with respect to FIG. 7. In the measurement and indicationroutine, the maximum value of an unbalanced condition of the spindle 3and the grinding wheel 4 and the position thereof arising from theunbalanced condition are detected on the basis of the vibration producedby the rotation of these rotating bodies 3, 4 with no weight attached,and the maximum unbalanced value is displayed on the numerical display16 while at the same time the index-position indicator 14 correspondingto the unbalanced position is intermittently energized or flickers.

After the display and indication have been stabilized, the operatorturns on the hold switch 19, which is confirmed by a step S8, and thedisplayed and indicated data are held. In a step S9, the amount andposition of the unbalanced condition with no weight attached, i.e., thevector data (→OA shown in FIG. 1b) of the unbalanced condition, aretemporarily stored in the RAM 26. Under this condition, the operatortentatively stops the rotation of the spindle 3 and the grinding wheel4, and a reference weight is attached to the grinding wheel 4 at anangular position (at θO° in FIG. 1b) from the original point. Then, theoperator shifts the condition setting switch 36 to the weight position,and starts rotating the spindle 3 again.

Thereafter, a step 11 confirms that the spindle 3 and the grinding wheel4 are stablized in their rotation. The program goes to a step 12 inwhich the vector (→OB in FIG. 1b) of an unbalanced condition of therotating bodies 3, 4 with the weight attached is measured and indicatedas in the step S7. In a following step S13, the vector (→OC in FIG. 1b)of the unbalanced condition with the weight attached is computed fromthe vector data with the weight attached and the vector data with noweight attached, and the computed vector is displayed on the numericaldisplay 16 while the index-position indicator 14 corresponding to theangular position (at θC° in FIG. 1b) of the vector is intermittentlyenergized. Then, when the turning-on of the hold switch 19 is confirmedin a step S14, the displayed and indicated data are held. The programnow returns to the step S2, thus completing the process in theadjustment mode.

Therefore, by subtracting the position (θ0°) where the weight isattached from the position (θC °) of the intermittently energizedindex-position indicator 14, the operator can recognize the positiondifference as a phase variation between the indicated unbalancedposition and the actual unbalanced position. The numerical ring 23 ofthe position controller 21 should then be turned for an angular intervalcorresponding to the phase variation to eliminate the phase deviation onthe indicator device 12 in the subsequent balance measuring operation sothat the unbalanced position indicated by the index-position indicator14 will be brought into exact conformity with the actual unbalancedposition. This results in an indication which is easier for the operatorto look at for allowing the operator to balance the grinding wheeleasily.

The measurement mode will be described with reference to FIG. 7.

After the indicated position has been corrected, and when themeasurement mode is selected by the mode selector switch 35, the programgoes from the NO side of the step S2 to the step S15 which confirms theoperation of the changeover switch 18. If an r.p.m. display mode isselected by the changeover switch 18, then a step S16 detects the r.p.m.of the spindle 3 based on the intervals of original-point detectingpulses generated by the original-point detecting sensor 10. After thedetected r.p.m. is displayed on the numerical display 16 in a step S17,control goes back to the step S15.

If the changeover switch 18 is not actuated and hence a deviationindicating mode is established in the step S15, then one of the high-,medium-, and low-gain setting switches 17 is turned on to select anamplification degree for the signal issued by the acceleration pickup 7,and the confirming indicator 17a corresponding to the actuated gainsetting switch 17 is energized in a step S19.

A step S20 detects the r.p.m. of the spindle 3 and the grinding wheel 4by measuring the intervals of the orignal-point detecting pulses fromthe original-point detecting sensor 10. A step S21 compares the measuredintervals of the original-point detecting pulses to ascertain whetherthe rotation of the spindle 3 and the grinding wheel 4 is stable or not.

In a step 22, the central frequency of the bandpass filter 33 of thefilter circuit 29 is brought into conformity with the frequencycorresponding to the r.p.m. of the spindle 3 as detected in the stepS20.

If the original point on the grinding wheel 4 is detected by theoriginal-point detecting sensor 10 in a step S23, then data items whichcan be processed by the A/D converter 28 in one revolution of thegrinding wheel 4, or 36 deviations that are as many as the number of theindex-position indicators 14, are detected, and the detected data itemsare stored in the RAM 26 in steps S24 through S27. If the original pointis detected in the step S26, then the program proceeds to a step S28 inwhich the total number of the detected deviation data items is dividedby the number of the index positions which are spaced 10° , or 36.Thereafter, the deviation data items for the respective index positionsare totaled in a step S29, and the sum is divided by the number of dataitems to compute primary average deviation data. The computed primaryaverage deviation data for the index positions is then stored in thedata area of the RAM 26 in a step S30.

A step S31 then ascertains whether the detection of the deviation dataand the storage thereof are repeated for a predetermined number oftimes. If not repeated, then the program returns through a step S32 tothe step S23, and if repeated, then the program goes to a step S33 inwhich the primary average deviation data for each revolution is read outof the RAM 26, the read data items are totaled, and the sum is dividedby the predetermined number to produce secondary average deviation data.The computed secondary average deviation data is then stored in the RAM26 for each index position in a step S34.

A step S35 selects the maximum deviation data and the index positionwhere the maximum deviation data is produced by comparing the secondaryaverage data items. In a step S36, the index position where the maximumdeviation data is produced is corrected on the basis of the datacorrected by operation of the position controller 21. In a step S37, themaximum deviation data is converted to a numerical value that can bedisplayed on the numerical display 16. A step S38 determines whether themaximum deviation is greater than a reference value or not. If themaximum deviation is greater than the reference value, the program goesto a step S39 in which the maximum deviation is displayed on thedeviation display 16 and the index-position indicator 14 correspondingto the position where the corrected maximum deviation is generated andis intermittently energized. At this time, other indicators 14 adjacentto the indicator 14 corresponding to the position where the maximumdeviation is produced are also energized. Since the central indicator 14flickers while the adjacent indicators 14 are continuously energized,the position where the maximum deviation occurs can easily be confirmed.

Then, if the hold switch 19 is detected as being turned on in a stepS40, then the displayed and indicated data is held, and the holdingcondition is indicated by the confirming indicator 19a which isenergized. If the hold switch 19 is not turned on, then the programreturns through a step S41 to the step S2 for repeating the aforesaidsteps.

If the maximum deviation is not greater than the reference value in thestep S38, i.e., if the spindle 3 and the grinding wheel 4 is judged asbeing balanced, then control goes to a step S42 in which the letters"GOOD" indicating the completion of the balancing operation aredisplayed on the numerical display 16. Thereafter, the program goes tothe step S40.

The numerical convertion in the step S37 can be effected by convertingthe data computed in the preceding step to relative values based on m·r(mass × radius ), acceleration, speed, displacement, or referencedeviation.

According to the balance indicating apparatus of the foregoingembodiment, the vector →OC in FIG. 1b represents not only the indicatedposition due to the weight having a weight W, but also the deviation asindicated of the weight. Therefore, by determining the ratio of thedeviation and the actual weight W, the deviation of the rotating bodycan be converted to a weight based on the determined ratio.Consequently, the unbalance of the rotating body can easily beeliminated by attaching the weight or balancing piece having theconverted weight to the angular position of the rotating body, whichcorresponds to the indicated index-position indicator 14.

As shown in FIG. 3, the angles of the index-position indicators 14 onthe indicator device 12 are progressively increased clockwise. However,the direction of rotation of the spindle in the grinding machine variesfrom type to type. To cope with this, a direction changeover switch maybe disposed on the indicator device 12, and may be selectively operateddependent on the direction of rotation of the rotating body to allowdata to be collected under the same condition. Thus, the balanceindicating apparatus can be used for balancing different rotating bodieswhich may vary in their direction of rotation.

In the foregoing first embodiment, the central frequency of thefrequency selecting means is automatically adjusted by the CPU 24.However, this frequency adjustment may be manually effected through amanual control dial.

The balance indicating apparatus of the present invention may bearranged to selectively detect and indicate the overall vibration of themachine tool and the vibration of the rotating body. With such a secondembodiment, a changeover switch 41 for selecting the overall vibrationor the rotative vibration is disposed on the indicating section 13 andconnected to an input terminal of the input/output interface 27, and anindicator 42 for selectively indicating the overall vibration or therotative vibration is disposed on the indicating section 13 andconnected to an output terminal of the input/output interface 27. Asillustrated in FIG. 9, the filter circuit 29 has a circuit 43 bypassingthe bandpass filter 33 with the changeover switch 41 connected in thecircuit 43. The changeover switch 41 is actuated by a changeover signalSG4 generated by the CPU 24 and applied via the input/output interface27.

Operation in the measurement mode of the balance indicating apparatusaccording to the second embodiment will be described with reference toFIG. 8.

Steps S15 through S19 in FIG. 8 are effected in the same manner as thesteps S15 through S19 in FIG. 7 for the balance indicating apparatus ofthe automatic adjusting type according to the preceding embodiment. Astep S20 ascertains whether a mode for detecting the vibration of therotating body is selected by the changeover switch 41. If not selected,i.e., if a mode for detecting the overall vibration is selected, thenthe mode for detecting the overall vibration is established in a stepS19a to override the operation of the bandpass filter 33 of the filtercircuit 29. Then, a pluraltiy of deviation data items produced by theoverall vibration on the head 6a are detected in a step S19b based onthe detected signal from the acceleration pickup 7. The maximumdeviation data value amont the deviation data items is then computed ineach time unit in a step S19c. Then, the computed data value isconverted to a numerical value that can be displayed, and the numericalvalue is displayed on the numerical display 16 in a step S19d.Thereafter, the program returns to the step S2. Therefore, the overallvibration of the machine tool can correctly be confirmed to facilitatedetermination of any abnormal vibration.

If the decision of the step S20 results in YES, i.e., if the mode fordetecting the vibration of the rotating body is selected, the mode fordetecting the vibration of the rotating body is established in a stepS21 to rely on the frequency selection by the bandpass filter 32. A stepS22 then ascertains whether the rotation of the spindle 3 and thegrinding wheel 4 is stable or not by measuring and comparing theintervals of original-point detecting pulses issued from theoriginal-point detecting sensor 10.

If the stable rotation of the spindle 3 and the grinding wheel 4 isconfirmed, then a step S23 detects the original point on the grindingwheel 4 through the original-point detecting sensor 10.

After the original point has been detected, the step S24 and followingsteps will be executed as in the operation of the preceding apparatus ofthe automatic adjusting type.

While the modes for detecting the overall vibration and the vibration ofthe rotating body are manually selected in the second embodiment, thesemodes may automatically switched on a time-sharing basis for displayingtwo data items at the same time. With such a modification, a display fordisplaying the overall vibration should be provided in addition to thedisplay for displaying the vibration of the rotating body.Alternatively, predetermined ranges may be established for ascertainingwhether the deviations due to the vibration of the rotating body and theoverall vibration are acceptable or not, and the results of thevibration acceptability may be displayed on respective displays withoutinvolving mode switching.

The present invention may be modified as follows:

(1) When the display "GOOD" is given after the balancing operation iscompleted, the result of balancing determination (if the unbalancedcondition is in the acceptable range or not) may be issued to anexternal circuit. The acceptable value setting may be varied.

(2) The deviation (noise level) may be measured while the rotating bodyof the machine tool is at rest. The noise level having the samefrequency as the r.p.m. of the rotating body may be measured even whenthe noise level is measured by utilizing the overall vibration of themachine tool. If the measured noise level exceeds the acceptable range,then an alarm may be indicated or issued to an external circuit forascertaining whether the rotating body can be measured for balancedcondition.

(3) The deviation may be displayed on an analog display such as a meteror the like, rather than the digital display, or may be displayed onboth digital and analog displays.

(4) In the balance indicating apparatus capable of automaticallyadjusting the central frequency, the central frequency of the filtercircuit 29 may be varied by the signal from the original-point detectingsensor without involving the CPU 24 (as by a voltage obtained byfrequency/voltage conversion). This alternative is advantageous in thatwhen the r.p.m. of the rotating body varies continuously, the ability ofthe central frequency to follow the r.p.m. of the rotating body isincreased, and the resolution of the central frequency is improved.

Although certain preferred embodiments have been shown and described, itshould be understood that many changes and modifications may be madetherein without departing from the scope of the appended claims.

What is claimed is:
 1. An apparatus for detecting and indicating thebalance of a rotating body in a machine tool, comprising:origin-pointdetecting means for detecting an origin-point on the rotating body;vibration detecting means for detecting vibration caused by anunbalanced condition of the rotating body; arithmetic means forcomputing, from the detected vibration, an off-center deviation of therotating body at each of a plurality of index positions on the rotatingbody which are angularly spaced from the origin-point as a reference;unbalance position indicating means for indicating an unbalance positionbased on the computed off-center deviations of the rotating body;display means for displaying an unbalance amount based on the computedoff-center deviations of the rotating body; and correcting means foradjusting and conforming the unbalance position indicated by theunbalance position indicating means exactly to the actual unbalanceposition of the rotating body, the arithmetic means comprising means forcomputing first vector data representing an unbalance position andamount on the rotating body without any weight thereon, second vectordata representing an unbalance position and amount on the rotating bodywith a weight attached thereto at an angular position from theorigin-point, and third vector data representing an unbalance positionand amount produced on the rotating body by the weight on the basis ofboth the first and second vectors; the adjustment by the correctingmeans being performed on the basis of the three vectors.
 2. An apparatusaccording to claim 1, further comprising mode selecting means forselecting one of an adjustment mode in which an adjustment of theunbalance position indicated by the unbalance position indicating meansis performed, and an unbalance measurement mode in which a measurementof the unbalance position and amount is performed
 3. An apparatusaccording to claim 2, further comprising condition setting means forsetting, in the adjustment mode, one of a first condition in which noweight is attached to the rotating body and a second condition in whichthe weight is attached to the rotating body, the arithmetic meanscomprising means for computing the first vector data on the rotatingbody in the first condition, and the second vector data on the rotatingbody in the second condition.
 4. An apparatus according to claim 3,wherein the unbalance position indicating means includes a plurality ofindicators arranged in an annular pattern so as to correspond torespective index positions and means for intermittently energizing aselected one of the indicators to indicate an index positioncorresponding to a deviation of maximum value among deviations for therespective index positions based upon computed deviations.
 5. Anapparatus according to claim 4, wherein the unbalance positionindicating means further includes means for continuously energizingindicators in a predetermined range of indicators adjacent theintermittently energized indicator.
 6. An apparatus for detecting andindicating the balance of a rotating body in a machine tool,comprising:origin-point detecting means for detecting an origin-point onthe rotating body; vibration detecting means for detecting vibrationcaused by an unbalanced condition of the rotating body; arithmetic meansfor computing, from the detected vibration, off-center deviation data ofthe rotating body at each of a plurality of index positions on therotating body which are angularly spaced from the origin-point as areference, the arithmetic means comprising means for computing as manydeviation data as are able to be processed in one revolution of therotating body from the origin-point and storing them in memory meansconnected to the arithmetic means, dividing the total number of thedeviation data by the number of the index positions, totaling themagnitudes of the deviation data for the index positions, and dividingthe total of said deviation magnitudes at said index positions by thenumber of deviation data for the index positions, thereby computing aprimary average deviation data and storing said primary averagedeviation data in the memory means, the arithmetic means comprisingmeans for totaling the primary average deviation data for the indexpositions in a predetermined number of revolutions of the rotating body,dividing the total deviation amount of the primary deviation data by thenumber of revolutions, and computing a secondary average deviation datafor the index positions, thereby selecting a maximum deviation data andan index position where the maximum deviation is produced by comparingthe secondary average deviation data for the index positions; unbalancedposition indicating means for indicating the index position where themaximum deviation is produced; and display means for displaying a valuecorresponding to the maximum deviation.
 7. An apparatus according toclaim 6, further comprising correcting means for adjusting andconforming the index position indicated by the unbalanced positionindicating means exactly to an actual unbalanced position of therotating body; mode selecting means for selecting one of an adjustmentmode in which an adjustment of the index position indicated by theunbalanced position indicating means is performed, and an unbalancemeasurement mode in which a measurement of an unbalanced position andamount is performed; the arithmetic means comprising means, in theadjustment mode, for computing first vector data representing anunbalanced position and amount on the rotating body without any weightthereon, second vector data representing an unbalanced position andamount on the rotating body with a weight attached thereto at an angularposition from the original point, and third vector data representing anunbalanced position and amount produced on the rotating body by theweight on the basis of both the first and second vectors, the adjustmentby the correcting means being performed on the basis of the threevectors.
 8. An apparatus according to claim 6, wherein the unbalancedposition indicating means includes a plurality of indicators arranged inan annular pattern so as to correspond to respective index positions,and means for intermittently energizing a selected one of the indicatorsto indicate the index position where the maximum deviation is produced.9. An apparatus according to claim 6, wherein the unbalanced positionindicating means further includes means for continuously energizingindicators in a predetermined range of indicators adjacent theintermittently energized indicator.
 10. An apparatus according to claim6, further comprising selecting means for selecting a signalcorresponding to a vibration of the rotating body among signals ofvibrations detected by the vibration detecting means, the selectingmeans including gain setting means for setting an amplification degreeof the signal detected by the vibration detecting means.
 11. Anapparatus according to claim 6, wherein the vibration detecting meansincludes a piezoelectric acceleration pickup detachably attached to adesired position of a frame of the machine tool.
 12. An apparatusaccording to claim 6, further comprising hold means for holding adisplay condition of the unbalanced position indicating means and thedisplay means.
 13. An apparatus according to claim 6, further comprisingchangeover means for selectively displaying either the valuecorresponding to the maximum deviation or an r.p.m. of the rotatingbody.